Inertia switches having holding means



Feb. 3, 1,970

w. w. H. cL-ARKE 3,493,701

INERTIA SWITCH HAVING HOLDING'MEANS Filed June 9, 1967 United States Patent O 3,493,701 INERTIA SWITCHES HAVING HOLDING MEANS Walter Wilson Hugh Clarke, Eversley, England, assignor to C. B. Associates Limited Filed June 9, 1967, Ser. No. 645,012 Claims priority, application Great Britain, June 10, 1966, 26,100/66 Int. Cl. H01h 35/02 U.S. Cl. ZOO-61.45 8 Claims ABSTRACT F THE DISCLOSURE An inertia switch comprises an operating mass, preferably a ball of magnetic material, normally held on a seating by a magnet. A sutlicient acceleration of the switch dislodges the mass and impels it to make or break a pair of contacts, preferably by axial movement between the contacts of an insulating peg having a conductive collar.

The invention relates to inertia switches, that is to say, switches operated by movement of the switch as a whole, for example by tilting, impact, vibration or acceleration.

lKnown inertia switches are costly to manufacture and in consequence have not been widely used in domestic appliances since their provision would necessitate a diS- proportionate increase in the retail price of the appliance. Such switches have many uses, for example to cut out the supply of electricity to a drive motor when a washing machine or spin drier exceeds a determined amplitude of oscillation due to overor eccentric-loading of the drum. Another use is to disconnect the electrical system of a vehicle, for example in the event of a crash.

The invention has among its objects to provide an inertia switch which can be produced cheaply.

According to the invention an inertia switch comprises a housing defining a seating, a magnet positioned adjacent the seating and an operating mass of magnetic material adapted to be held on the seating by the magnet until dislodged by an acceleration of determined magnitude applied to the switch, thereby causing the mass to move an elongated member axially to make or to break a pair of electrical contacts. Preferably the operating mass is spherical and located on a frusto-conical seating, the magnet being adjacent the smaller face of the frustum.

Advantageously the elongated member is a peg of electrically insulating material having a collar of electrically conducting material thereon, movement of the peg axially being effective to move the collar to engage or disengage a pair of contacts co-operatng therewith to -make or break an electrical circuit.

The frusto-conical seating advantageously tapers inwardly with the magnet mounted axially thereof so that the spherical operating mass is held by the magnet within the frusto-conical seating. The seating is preferably so formed that an air gap exists between the magnet and the operating mass.

According to one embodiment of the invention, the peg member is positioned in a bore in the end face of a sleeve of plastics or other non-magnetic material and engages a magnet assembly with a snap action. Spring members passing between the sleeve and the magnet assembly engage opposite sides of the peg, the spring members being so spaced apart that the operating mass cannot engage both spring members at the same time. If the magnet assembly and/or the sleeve are electrically conductive, the spring members must be insulated therefrom.

Under vibration or acceleration of the switch to an extent exceeding the retention force of the magnet the operating lmass leaves the seating and strikes the peg. Upon being struck, the peg moves axially of the switch to cause 3,493,701 Patented Feb. 3, 1970 ICC the spring members to slide on to or off an electrically conductive collar on the peg, thereby making or breaking a circuit.

The operating mass may be provided in other than a spherical form, for example as a cylinder located on a recessed circular seating. In this case the switch will only respond to an acceleration in the direction of its axis. Furthermore, 4by small modifications of the switch additional contacts may be operated if required.

Two embodiments of the invention are diagrammatically illustrated by way of example in the accompanying drawings, which are sections through inertia switches according to the invention:

FIGURES l and 2 illustrate two central cross-sectional Views of a switch with normally closed contacts, shown set in FIGURE 1 and tripped in FIGURE 2;

FIGURE 3 illustrates a central cross-sectional view of a switch with normally open contacts shown in the set position.

The switch shown in FIGURES l and 2 is formed with a sleeve-like housing 1 and a seating assembly 2 engaged therewith, formed by injection moulding from a plastics material. A cylindrical magnet 3 is secured in a bore of a seating assembly 2 adjacent a frusto-conical seating 4, a ball 5 of magnetic material being held in the frustoconical seating by the attraction of the magnet 3. A peg 6 of plastics material has a copper collar 7 secured thereon and is provided in a bore, co-axial with the axis of the magnet 3, in an end face of the sleeve 1. There is a small gap, of the order of 1/16 between the ball 5 and the peg 6. Contact springs 8 passing between the sleeve 1 and the seating assembly 2 engage the collar 7 and, for eX- ample, complete the circuit of a vehicles electrical systern or carry the motor current for a washing machine drive.

Upon vibration or acceleration of the switch in a plane at right angles to its axis, the ball 5 is shaken loose from the seating 4 and rides up the seating to strike the end of the peg `6, knocking it axially outwardly to the position shown in FIGURE 2, so that the springs 8 engage with the axially outward face of cap 9 on the end of the peg 6, and are insulated one from the other. The small gap between ball and peg allows the ball to build up momentum before having to overcome the frictional resistance to sliding of peg 6. The portion of the peg 6 between the collar 7 and the cap 9 is tapered as shown so that the action of the springs 8 assists the movement of the peg 6, the tapered portion also forming a holding recess in which is positioned the ends of the springs 8 when peg 6 is moved outwardly. To re-set the switch the peg is pressed axially inwardly by means of a block 10 thus pressing the ball 5 into its seating 4 and making electrical contact between the springs 8 by means of the collar 7. The end face of the cup is to some extent resilient, thereby permitting a gap between the ball 5 and cap 9 while allowing the ball 5 to be pressed firmly into its seating.

As shown in FIGURE 3 the conductive collar 7 can if required be provided on the portion of the peg 6 immediately behind the cap 9 so that a connection is made upon outward movement of the peg 6.

I claim:

1. An inertia-operated switch device, comprising:

housing means having seating means including a seat formed therein;

magnet means mounted in said seating means and positioned adjacent said seat;

an actuating member movably mounted on said housing means for movement between first and second positions, said actuating member having a portion disposed opposite said seat with said actuating member being normally maintained in said first position, movement of said actuating member to said second position causing said portion to be moved away from said seat;

contact means including a pair of relatively movable electrical contacts coacting with said actuating member for creating an electrical circuit when said actuating member is in one of said positions;

an inertia mass movably disposed within said housing means between said seat and said portion of said actuating member, said inertia mass being normally magnetically attracted to said magnet means so as to be held in engagement with said seat whereby imposition of a predetermined shock force on said switch device causes said inertia mass to be moved away from said seat so as to contact said portion of said actuating member and move said actuating member from said rst position to said second position; and

said contact means and said actuating member including means for releasably holding said actuating member in said second position after it has moved to said second position.

2. A switch device according to claim 1, wherein said last-mentioned means includes resilient means coacting with said contacts and a recess formed in the actuating member whereby said contacts are resiliently urged into 1 said recess for engaging and holding said actuating member in said second position.

3. A switch device according to claim 1, wherein said actuating member includes an annular recess thereon, and wherein said releasable holding means includes a pair of elongated spring members having end portions resiliently urged into engagement with said actuating member so as to be positioned within said recess when said actuating member is in said second position.

4. A switch device according to claim 3, wherein said pair of elongated spring members are electrically conductive and said end portions comprise a pair of electrical contact portions, and said actuating member has an electrically conductive means ixedly secured thereto and contacted by said pair of contact portions when said actuating member is in said one of said first and second positions.

5. A switch device according to claim 2, wherein said seat is frusto-conical and said magnet means is positioned adjacent the apex of said seat, and wherein said inertia mass is of a spherical configuration.

16. A switch device, comprising:

housing means including an elongated tubular portion having a base member, said base member having an opening extending therethrough;

a seat member iixedly secured to one end of said tubular member, said seat member having a bearing surface thereon positioned within the interior of said housing means yand spaced opposite from said openlng;

magnet means fixedly secured to Said seat member and having a portion disposed adjacent said bearing surface;

an elongated actuating member slideably mounted on said housing means and disposed within and extending through the opening formed in said base member, said actuating member being movable relative to the elongated direction of said housing means between rst and second positions, said actuating member further having an end portion disposed within the interior of said housing means between said base member and said bearing surface, and said actuating member including electrically conductive means disposed within the interior of said housing means when said actuating member is in at least one of said positions;

electrical contact means mounted on said housing means and adapted to coact with the electrically conductive means of said actuating member, said electrical contact means including a pair of elongated resilient members of electrically conductive material having free end portions dening a pair of spaced contacts with said free end portions being disposed within the interior of said housing means within the space between said base member and said seat member, and the contacts on said free end portions being adapted to resiliently contact the electrically conductive means of said actuating member when said actuating member is in said one position; and

an inertia member movably disposed within the interior of said housing means between said bearing surface and the end portion of said actuating member, said inertia member being normally magnetically attracted to said magnet means and held in bearing engagement with said bearing surface, movement of said inertia member away from said bearing surface causing same to contact the end portion of said actuating member so as to move same from said first position to said second position.

7. A switch device according to claim 6, wherein said contacts are resiliently urged into contact with said actuating member when said actuating member is in both said rst and said second positions.

8. A switch device according to claim 7, wherein said end portion of said actuating member is formed with a tapered surface thereon, said contacts being resiliently urged into engagement with said tapered surface to assist in moving said actuating member from said rst position to said second position.

References Cited UNITED STATES PATENTS 3,270,159 8/1966 Soos 20D-61.45 XR 2,056,494 10/1936 Tucker et al. 20G-61.45 2,552,665 5/1951 Cirone 340--262 3,165,574 l/1965 Carling.

ROBERT K. SCHAEFER, Primary Examiner M. GINSBURG, Assistant Examiner U.S. Cl. X.R. 20G-61.53 

